Method and apparatus for heat treating metal articles



July 5, 1927. 1,634,319

T. F. CALLAGHAN METHOD AND APPARATUS FOR HEAT TREATING METAL ARTICLES Filed Oct. 27, 1924 2f; o FE1-1 Wwf@ Patented July 5, 1927. UNITED, STATES THOMAS r. CALLAAGIIAN, or BELLEFONTE, PENNSYLVANIA, ASSIGNoR 'ro EBWIN c.

UIHLEIN, oF MILWAUKEE; WISCONSIN.

PATENTJ oFIf-lcs.

METHOD .AND APPARATUS FOR HEAT TREATING METAL ARTICLES.v

Application filed October 27, 1924. Serial No. 746,094.

Thepresent invention relates to a method and apparatus which is particularly designed for the hea't treatment of metal articles.

One of the obiects of the invention is to perform the heat treating of metal articles by enclosing the articles to be heated in an enclosure under such conditions that the oxidation of the articles during the heat treating process and subsequent thereto will be substantially eliminated, or at least held to a minimum amount.

i A further object of theinvention is to provide a method and construction by which the articles are quenched whilemaintained in such condition that they are free from influences of oxygen or oxidizing actions.

Other objects of the invention 'will' appear as the description proceeds.

Reference should be had to the accompanying drawings, in which Fig. l is an elevation of an apparatus embodying the present invention, and in which the method herein described may be performed. Fig. 2 is a section upon the line 2-2 of Fig. 1.

It may be generally stated that the method and the apparatus for' accomplishing the method which are hereindescribed are for the purpose of heat treating metal articles so that while they are being heat treated $0 they will be maintained under conditions which will exclude air or other oxidizing influence, and subsequent to the heating operation the articles .may be plunged in a quenching bath while still maintained out of contact with air.

This method is of particular importance in connection with certain classes of dies, tools. and other articles of similar nature in which the dies or tools are brought to their proper final shape while the metal is soft, and it is very desirable that when they are hardened' they shall not be covered with an undue amount of scale, which always is the consequence when these articles are heat` treated by usual methods,l or where they are case-hardened.l All these methods of heat treating which have ybeen mentioned invariably produce a more or less heavy scale which requires considerable refinishing and additional work upon such articles after they have been heat treatedor case-hardened.

It may be stated that the method of heat treating which is herein proposed consists in conning the articles to be heat treated within a suitable enclosure from which enclosure, at the time of the heating, the air is removed. This does not mean necessarily that there is a perfecty vacuum formed, but

it-is entirely feasible by the use of commercial exhaust pumps which are now known, to remove at least the major portion of the air from such a container so that the oxidizing action which could take place during the heat treating action would be almost negligible, or atleast, it would be so small as to require a minimum amount of additional work in reinishing the article after the heat treating process.

The second step in the method which is herein proposed consists in quenching the articles which have been heat treated in a suitable quenching bath. while still maintaining the condition of vacuum or partial vacuum so as to protect the articles against oxidation until they are immersed in the quenching bath. After the quenching operation the temperature ofthe articles is sufficiently reduced so that the danger of oxidizing action thereafter is removed.

In the present invention one form of apparatus )for carrying out the method is shown, although ne limitation is intended with'respect to the process bythe' disclosure and description of the following apparatus.

In the drawings, 1 indicates an enclosure which may be cylindrical, rectangular, elliptical, or any desired shape, and comprises a bottom wall and sidewalls which are integral and nonporous. This enclosure may be formed of metal. At the upper end of the bodyl there is anoutw'ardly extending anflange 3 formed on a. dome-shaped cover member 4. It will doubtless be desirable to insert a packing ring, such as metal, between the flanges 2 and 3 in order to secure a hermeticallyf'tight joint. The cover member 4 may be held onto the body 1 by any suitable fastening means, as by means of the nut and bolt structure which is indicated at ,nular ange 2 and this co-operates witha lwhich is Shwn at s, which 'plate is in wm supported by an angle bracket 9, these plates and angle irons being distributed at suitable intervals beneath the shell 6 in order to support it.

Upon the wall of insulating material 7 there will be carried, in any suitable fashion, resistance material, such as indicated at 10,

which will develop the required heat when a suitable electric current the resistance.

Upon the inside of the cover 4 there isa 1s passed through cap member which is generally designated at l1. This cap member has an outerportion which may be of metal, and an inner portion 12 which may be of heat resisting.

' material, the heat resisting material forming an inner lining. The member 11 is supported from the cover 4 by means of links13 or any other Suitable manner, and the arrangement is tion where it extends through the cover 4,'

as indicated at 16, and it also includes right angled extending portions 17 which may be four, as shown in the drawing, or any other suitable number. Within the tubular portion 15 there is an inner pipe 18 which at its lower end has right angularly extending pipes 19, each of the pipes 19 extending intoone of the extensions end of the tubular member 15 there is an outlet pipe 20, and communicating with the inner pipe 18 there is an inlet pipe 21. Water may be circulated through the pipe 21. The pipe 18 and the branch pipes 19, and the return, will be through the extension 17 the tubular member 15, and the exit pipe 20. Thustherewill be maintained a circulation of cooling water which will be sutlicient to prevent melting or ill effects de to the heat within the chamber.

The plates 8 have pivotally connected thereto two swinging door members 22 and 23, these door members cooperating by means of an overlay, as indicated at 24. These gate members 22, 23, are mounted upon rods, one-of which is indicated at 25, which extend upon the outside of the enclosure memberl, and there may be operated by suitable means to open or close the same, as may be desired. Y

the lower portion of the enclosure member 1 there will be confined a bo'dy of p quenching liquid, as indicated at 26. This yas shown in` the drawing,

17. At the upper liquid maybe introduced or taken out by means of the valved pipe 27.

In order to agitate the quenching mediun, a stirring blade 28 is provided, the shaft of which extends upon the outside of the member 1, andmay be suitably rotated.

Within the lower portion of the member 1 there extends a coil of pipe, such as indicated at 29, through which a cooling medium may be circulated in order to maintain the temperature of the quenching medium to thatwhich may be desired.

Adjacent the upper end of the enclosing body 1 there isa pipe 30 which is adapted to be connected with a suitable exhaustingpump or other apparatus, by which air may be exhausted from the interior of the enclosing member 1. No particular apparatus need be shown as apparatus which will accomplish this function is well known in the art. i i

The articles which are to be heat treated are carried by the extensions 17, these forming a support for suchl articles in approximately the middle portion of the heating zone of the apparatus.

When articles to be heat treated are suitably supported upon the extension 17 and the cover 4 is brought into closed position,

the air maybe exhausted through the exhaust pipe 30, and the electric current causedA to pass through the resistance elements 19. The heat which will thus be generated will be reflected from the walls toward the center of the furnace, and also from the top of the furnace, thus enabling an exceedingly high temperature for heat .treating purpose to be obtained.

Due to the fact' that the air is exhausted l from thechamber in which the'heat treating is being effected, there can be no oxidizing action except to the very limited extent permitted by exhausted. But this, is a function of the which is obtainedl When the heating as will be clearly seen, degree of exhaustion and may bey controlled. of the metal .articles is the presence of such air as is not completed, the closure members 22 and 23 are opened and the supports 17 with the t-ubular member 15 are lowered into the quenching bath, which as will be clearly seen, is also under sub-atmospheric conditions, so that the non-oxidizing conditions are maintained\during the quenching operation.

vAs soon as the quenching is completed the cover 4 may be removed and with it the tubular member 15 and the support 17 and the articles which have been heat treated.

It will readily be appreciated-that in the practice of the method which has been described, that if it be desired, carbonizing gases may be introduced into the furnace or the container, as it has heretofore been called, so that the metal articles being heat treated may be subject to the action of the carbonizing gases at the same time they are heated.

It is also Within the province ofy the present inventionzto supply an atmosphere of an inert gas after the air has been exhausted therefrom.y Such inert gases will be free from any *oxygen or oXidizing element, so that no oxidation of metal articles Within the furnace Will beeffeeted.

Having described my invent-ion, I claim 1. In an apparatus of the character" described, the combination with a container, a closure member for said container, a shell Within the container which is spaced from the Wall of the container, and means for supporting said shell, a refractory lining upon the inner Wall of the shell, electric resistance members carried by the said refractory Wall, a cap co-operating With the said shell and refractory lining upon the inner Wall of said cap, means through which air may be exhausted from the interior of the container` a movable supporting means Within the said container for supporting articles to be heat treated, a quenching bath compartment- Within said container the said movable supporting means being adapted to more into said quenching bath compartment.

2. In apparatus of the character described` the combination of a container, one portion of said container serving as a quenching bath compartment, another portion of said container'having a shell Within the same, said shell being spaced from the -Wall of the container, means for supporting said shell Within the container, a suitable refractory lining upon the inner Wall of said shell` electric resistance members Within the shell, a. capi cil-operating with said shell said cap having a suitable refractory lining` a movable member for supporting articles to be heat treated` said movable member having portions which extend through the said cap and said closure member for the container said movable member being adapted to move into the quenching compartment.

3. In apparatus of the character described, the combination With a container having at the lower portion thereof a compartment adapted to contain a quenching medium, closure members above said compartment, a shell Within said container and spaced from the Wall thereof above the said quenching compartment, a refractory lining upon the interior of said shell, electrical resistance elements Within said shell, a cap co-operating with the said shell at the upper end thereof said cap having a refractory lining upon the inner Wall thereof, a closure member for the said container, a conduit through which air may be exhausted from the container, movable means for supporting articles to be heat treated, said movable means being capable of being moved from the heat compartment to the quenching compartment.

4. In apparatus of the character described. the combination in a container, a portion otl said container being adapted to contain a quenching medium, cooling means associated With the container for maintaining the quenching media at desired temperature conditions. agitating means associated with said compartment of the container for agitating the quenching media, a shell supported Within said container above the quenching compartment said shell being spaced from the Wall of the container, means for supporting the shell, a lining of refractory material upon the inner Wall of the shell, a cap member (zo-operating with the upper end of said shell said cap member having a refractory lining upon the innersurface thereof, a closure mem-y ber for said container, a conduit communieating with the interior of the container b v Which air may be exhausted therefrom, a movable supporting member having` portions extending through the cap and the closure for the container said member being adapted to support articles to be heat treated. said member being movable from the heat treating con'ipartment to the quenching compartment.

Intestimony whereof, I hereunto affix my signature.

THOMAS F. CALLAGHAN. 

